A technique disclosed by Patent Document 1 is known as an electronic expansion valve. In this technique, a valve body is provided with a surface substantially parallel to a refrigerant flow path in order to improve the controllability of the amount of refrigerant flow in a small flow range.
When the operation of an air conditioner is in a stable period, the amount of refrigerant flow is required to be slightly adjusted. However, if an increase in the opening area with respect to the minimum movement range of the valve body is great, it will be difficult to increase or decrease the amount of refrigerant flow only slightly. When the amount of refrigerant flow varies exceeding a control allowable range, the valve body is repeatedly moved forwardly or backwardly to finely adjust the opening degree.
In a conventional electronic expansion valve, it is possible to control the amount of refrigerant flow in a small flow range by employing the aforementioned arrangement. However, a basal part of the valve main body is parallel to the side surface of the refrigerant flow path over a predetermined distance, and therefore the opening area can hardly vary even if the valve body moves within this range. In other words, the amount of refrigerant flow hardly varies in some movement places of the valve body, and it is impossible to finely adjust the amount of refrigerant flow.